1. Field of the Invention
The present invention relates to an orbiting vane compressor, and, more particularly, to a capacity-changing unit disposed in an orbiting vane compressor, which compresses refrigerant gas introduced into a cylinder through an orbiting movement of an orbiting vane in the cylinder, for easily changing capacity of the orbiting vane compressor in a mechanical bypass fashion without interrupting the operation of the orbiting vane compressor.
2. Description of the Related Art
Generally, an orbiting vane compressor has inner and outer compression chambers formed in a cylinder through an orbiting movement of an orbiting vane in the cylinder. FIG. 1 is a longitudinal sectional view illustrating the overall structure of a conventional orbiting vane compressor. The conventional orbiting vane compressor shown in FIG. 1 is a hermetically sealed type low-pressure orbiting vane compressor that can be applied to a refrigerator or an air conditioner as a hermetically sealed type refrigerant compressor, which has been proposed by the applicant of the present application.
As shown in FIG. 1, a drive unit D and a compression unit P are mounted in a shell 1 while the drive unit D and the compression unit P are hermetically sealed. The drive unit D and the compression unit P are connected to each other via a vertical crankshaft 8, the upper and lower ends of which are rotatably supported by a main frame 6 and a subsidiary frame 7, such that power from the drive unit D is transmitted to the compression unit P through the crankshaft 8.
The drive unit D comprises: a stator 2 fixedly disposed between the main frame 6 and the subsidiary frame 7; and a rotor 3 disposed in the stator 2 for rotating the crankshaft 8, which vertically extends through the rotor 3, when electric current is supplied to the rotor 3. The rotor 3 is provided at the top and bottom parts thereof with balance weights 3a, which are disposed symmetrically to each other for preventing the crankshaft 8 from being rotated in an unbalanced state due to a crank pin 81.
The compression unit P comprises an orbiting vane 5 having a boss 55 formed at the lower part thereof. The crank pin 81 is fixedly fitted in the boss 55 of the orbiting vane 5. As the orbiting vane 5 performs an orbiting movement in a cylinder 4, refrigerant gas introduced into the cylinder 4 is compressed. The cylinder 4 comprises an inner ring 41 integrally formed at the upper part thereof while being protruded downward. The orbiting vane 5 comprises a circular vane 51 formed at the upper part thereof while being protruded upward. The circular vane 51 performs an orbiting movement in an annular space 42 defined between the inner ring 41 and the inner wall of the cylinder 4. Through the orbiting movement of the circular vane 51, inner and outer compression chambers are formed at the inside and the outside of the circular vane 51, respectively. Refrigerant gases compressed in the inner and outer compression chambers are discharged out of the cylinder 4 through inner and outer outlet ports 44 and 44a formed at the upper part of the cylinder 4, respectively.
Between the main frame 6 and the orbiting vane 5 is disposed an Oldham's ring 9 for preventing rotation of the orbiting vane 5. Through the crankshaft 8 is longitudinally formed an oil supplying channel 82 for allowing oil to be supplied to the compression unit P therethrough when an oil pump 83 mounted at the lower end of the crankshaft 8 is operated.
Unexplained reference numeral 11 indicates an inlet tube, 12 a high-pressure chamber, and 13 an outlet tube.
When electric current is supplied to the drive unit D, the rotor 3 of the drive unit D is rotated, and therefore, the crankshaft 8 is also rotated. As the crankshaft 8 is rotated, the orbiting vane 5 of the compression unit P performs an orbiting movement along a radius of the orbiting movement while the crank pin 81 of the crankshaft 8 is eccentrically fitted in the boss 55 formed at the lower part of the orbiting vane 5.
As a result, the circular vane 51 of the orbiting vane 5, which is inserted in the annular space 42 defined between the inner ring 41 and the inner wall of the cylinder 4, also performs an orbiting movement to compress refrigerant gas introduced into the annular space 42. At this time, the inner and outer compression chambers are formed at the inside and the outside of the circular vane 51 in the annular space 41, respectively. Refrigerant gases compressed in the inner and outer compression chambers are guided to the high-pressure chamber 12, which is disposed above the cylinder 4, through the inner and outer outlet ports 44 and 44a of the cylinder 4, which communicate with the inner and outer compression chambers, respectively, and are then discharged out of the orbiting vane compressor through the outlet tube 13. In this way, high-temperature and high-pressure refrigerant gas is discharged.
FIG. 2 is an exploded perspective view illustrating the structure of the compression unit P shown in FIG. 1.
In the compression unit P of the orbiting vane compressor, as shown in FIG. 2, the orbiting vane 5, which is connected to the crankshaft 8, is disposed on the upper end of the main frame 6, which rotatably supports the upper part of the crankshaft 8. The cylinder 4, which is attached to the main frame 6, is disposed above the orbiting vane 5. The cylinder 4 is provided at a predetermined position of the circumferential part thereof with an inlet port 43. The inner and outer outlet ports 44 and 44a are formed at predetermined positions of the upper end of the cylinder 4.
At a predetermined position of the circumferential part of the circular vane 51 of the orbiting vane 5 is formed a through-hole 52 for allowing refrigerant gas introduced through the inlet port 43 of the cylinder 4 to be guided into the circular vane 51 therethrough. The through-hole 52 is opened to the upper part of the circular vane 51 and to a slider 54. The slider 54 is disposed in an opening 53, which is formed at another predetermined position of the circumferential part of the circular vane 51 of the orbiting vane 5 while being adjacent to the position where the through-hole 52 is formed, for maintaining the seal between the inner and outer compression chambers of the circular vane 51.
FIG. 3 is a cross-sectional view illustrating the compression operation of the conventional orbiting vane compressor shown in FIG. 1.
When the orbiting vane 5 of the compression unit P is driven by power transmitted to the compression unit P from the drive unit D through the crankshaft 8 (See FIG. 1), the circular vane 51 of the orbiting vane 5 disposed in the annular space 42 of the cylinder 4 performs an orbiting movement in the annular space 42 defined between the inner wall of the cylinder 4 and the inner ring 41, as indicated by arrows, to compress refrigerant gas introduced into the annular space 42 through the inlet port 43.
At the initial orbiting position of the orbiting vane 5 of the compression unit P (i.e., the 0-degree orbiting position), refrigerant gas is introduced into an inner suction chamber A1 as the inner suction chamber Al communicates with the inlet port 43, and compression is performed in an outer compression chamber B2 of-the circular vane 51 while the outer compression chamber B2 does not communicate with the inlet port 43 and the outer outlet port 44a. Refrigerant gas is compressed in an inner compression chamber A2, and at the same time, the compressed refrigerant gas is discharged out of the inner compression chamber A2 through the inner outlet port 44.
At the 90-degree orbiting position of the orbiting vane 5 of the compression unit P, the compression is still performed in the outer compression chamber B2 of the circular vane 51, and almost all the compressed refrigerant gas is discharged out of the inner compression chamber A2 through the inner outlet port 44. At this stage, an outer suction chamber B1 appears so that refrigerant gas is introduced into the outer suction chamber B1 through the inlet port 43.
At the 180-degree orbiting position of the orbiting vane 5 of the compression unit P, the inner suction chamber A1 disappears. Specifically, the inner suction chamber A1 is changed into the inner compression chamber A2, and therefore, compression is performed in the inner compression chamber A2. At this stage, the outer compression chamber B2 communicates with the outer outlet port 44a. Consequently, compressed refrigerant gas is discharged out of the outer compression chamber B2 through the outer outlet port 44a. 
At the 270-degree orbiting position of the orbiting vane 5 of the compression unit P, almost all the compressed refrigerant gas is discharged out of the outer compression chamber B2 of the circular vane 51 through the outer outlet port 44a, and the compression is still performed in the inner compression chamber A2 of the circular vane 51. Also, compression is newly performed in the outer suction chamber B1. When the orbiting vane 5 of the compression unit P further performs the orbiting movement by 90 degrees, the outer suction chamber B1 disappears. Specifically, the outer suction chamber B1 is changed into the outer compression chamber B2, and therefore, the compression is continuously performed in the outer compression chamber B2. As a result, the orbiting vane 5 of the compression unit P is returned to the position where the orbiting movement of the orbiting vane 5 is initiated. In this way, a 360-degree-per-cycle orbiting movement of the orbiting vane 5 of the compression unit P is accomplished. The orbiting movement of the orbiting vane 5 of the compression unit P is repeatedly performed in succession.
Meanwhile, a refrigerating apparatus, such as a refrigerator, or an air-conditioning apparatus, such as an air-conditioner, is operated in economic operation mode where the operation of the compressor is interrupted when the interior temperature of the refrigerator or the room temperature is decreased to reach a predetermined level, and the operation of the compressor is resumed when the interior temperature of the refrigerator or the room temperature is increased above the predetermined level. In the economic operation mode, the operation of the compressor is alternately interrupted and resumed. Generally, much more electric power is consumed when the compressor is initiated or resumed after being interrupted than when the compressor is operated in a normal state. When the operation of the compressor is abruptly interrupted and then resumed, components of the compressor may wear out quickly due to interference between load of compressed air in the compressor and the components of the compressor, and therefore, the service life of the compressor may be shortened.
Consequently, it is necessary to change the capacity of the compressor without alternately interrupting and resuming the operation of the compressor. The capacity of the compressor may be changed in an inverter system, i.e., by controlling the number of rotations of the drive unit of the compressor, such as a motor. However, this inverter system requires various electric circuit control devices and relevant parts, which are very expensive. As a result, the manufacturing costs of the compressor are increased, and therefore, the price competitiveness of the compressor is lowered.